In a spacecraft as well as other situations where micro-organism control of drinking water is desired, iodine is a suitable agent. Iodine has several notable characteristic advantages as a micro-organism control and is effective against a broad spectrum of organisms. Ordinarily, in a spacecraft operation, it is desirable to maintain low weight requirement and low electrical power consumption. In this invention the valve operates at 10 mWatts and 5 ma. The spacecraft uses recycled water. The iodine system is superior to pasteurization on the basis of weight, volume, cost and power consumption.